Wicket bags are widely used by high-speed automatic equipment designed for packaging applications in many industrial fields such as agricultural, food such as cheese and bakery, hardware items and retail products industries. Typically, a wicket bag is a bag made of soft plastic material such as polyethylene, and provided with an upper tab adjacent the mouth of the bag, which tab is provided with a plurality of holes adapted to be received in corresponding wicket or pins provided on a holder capable of supporting stack of such wicket bags. The bag tab is adapted to be separated from the useful part of the bag, though a partially cut junction, generally after the bag filling operation, and before the bag closing operation usually performed using twist tie, clip, tape closure or heat-sealing. To provide high-speed operation, known automatic packaging equipment using wicket bags generally make use of complex systems for handling the wicket bags being transported to the desired working position. Such known automatic wicket bag handling systems are disclosed in many patent prior patent documents: U.S. Pat. Nos. 6,662,532 B1; 6,550,226 B1; ,696,146; 4,124,966 and CA 2,249,849 A1. Amongst the handling operations generally involved, an important one consists of reliably forming at high speed a neck portion at a precise location on the bag with high repeatability.